Fundamentals of signal processing devices

A novel acoustoelectric device capable of storing large bandwidth analog signals and correlating the stored signal with other signals is described. The device uses charge storage in an array of Schottky diodes on a silicon strip mounted adjacent to a lithium niobate surface-wave delay line. The paper emphasizes experimental results characterizing the device in terms of storage capacity, storage time, linearity, and efficiency. Based on the experimental data, a short discussion is given on anticipated performance limitations.

The Schottky diode acoustoelectric memory and correlator&#8212;A novel programmable signal processor

Abstmct-The use of SAW convolvers in both communication and signal-processing applications is discussed, with special emphasis given to their role in spread spectrum communications. In particular, noise analysis of the convolver will be presented, which accounts for both external and internal sources of noise.

The Use of SAW Convolvers in Spread-Spectrum and Other Signal-Processing Applications

A technique for receiving radar pulse trains is presented [which can be of a variable format in the sense that they vary from pulse to pulse]. The heart of the receiver is a sufrace ascoustic wave (SAW) convolver. In addition to prsenting experimental results for variable format waveform reception, it is shown that the convolver can easily generate ambiguity functions for virtually any waveform, and specific results for signals such as Barker codes and linear FM (chirp) waveforms are presented.

Variable Format Radar Receiver Using a SAW Convolver

: The techniques recently developed for fabricating, inspecting, assembling and packaging silicon-on-LiNbO3 acoustoelectric devices, such as amplifiers, convolvers and memory correlators, will be presented. This will include: description of the lithographic and ion beam etching techniques employed in making the spacer posts, demonstration of the techniques used for eliminating dust and achieving uniform gaps, inspection methods, and several examples of packages. Experience to date indicates that the techniques for making gap-coupled structures are reliable, and lend themselves to widespread application. (Author)

Techniques for Making Gap-Coupled Acoustoelectric Devices

: Silicon Schottky-diodes have been used to store images of surface acoustic waves propagating on lithium niobate. These images were subsequently employed to provide programmable matched filter or coherent integration fuctions. This technique could also be used to holographically store a large number of acoustic beams to provide a storage capacity as large as 100,000 bits of information. The basic storage element is a Schottky diode with an overlay of polysilicon. Many such diodes are arrayed on centers which are less than an acoustic wavelength apart. When the acoustic signal is in position beneath the diode array, the diodes are forward-biased for several nsec, which causes charge to flow to the diode contact in response to the piezoelectric field of the surface wave. These charges diffuse into the polysilicon in several microseconds, after which a succeeding signal can be overlayed in the array. These charges, which are an image of the acoustic signal are retained in the polysilicon for as long as 100 ms. The stored image is proportional to the acoustic signal in every respect, including the amplitude, phase and wavefront details. This procedure could be repeated for many acoustic beams, and a subsequent signal along a given stored beam causes an electrical signal to appear across the silicon-lithium noibate composite which is proportional to the cross-correlation of the signal with all stored images. This gives rise to the desired output signal, plus undesirable cross-talk signals. Also the desired signal is relatively weak, and its signal-to-noise ratio needs to be increased with a coded interrogating signal and a matched filter. (Author)

K. Ingebrigtsen

Papers

Holographic Storage of Acoustic Surface Waves with Schottky Diode Arrays